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1 /*	$OpenBSD: print-gre.c,v 1.6 2002/10/30 03:04:04 fgsch Exp $	*/
2 
3 /*
4  * Copyright (c) 2002 Jason L. Wright (jason@thought.net)
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. All advertising materials mentioning features or use of this software
16  *    must display the following acknowledgement:
17  *	This product includes software developed by Jason L. Wright
18  * 4. The name of the author may not be used to endorse or promote products
19  *    derived from this software without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
23  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
24  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
25  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
26  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
27  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
29  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
30  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
31  * POSSIBILITY OF SUCH DAMAGE.
32  */
33 
34 /* \summary: Generic Routing Encapsulation (GRE) printer */
35 
36 /*
37  * netdissect printer for GRE - Generic Routing Encapsulation
38  * RFC1701 (GRE), RFC1702 (GRE IPv4), and RFC2637 (Enhanced GRE)
39  */
40 
41 #ifdef HAVE_CONFIG_H
42 #include "config.h"
43 #endif
44 
45 #include <netdissect-stdinc.h>
46 
47 #include <string.h>
48 
49 #include "netdissect.h"
50 #include "addrtostr.h"
51 #include "extract.h"
52 #include "ethertype.h"
53 
54 static const char tstr[] = "[|gre]";
55 
56 #define	GRE_CP		0x8000		/* checksum present */
57 #define	GRE_RP		0x4000		/* routing present */
58 #define	GRE_KP		0x2000		/* key present */
59 #define	GRE_SP		0x1000		/* sequence# present */
60 #define	GRE_sP		0x0800		/* source routing */
61 #define	GRE_RECRS	0x0700		/* recursion count */
62 #define	GRE_AP		0x0080		/* acknowledgment# present */
63 
64 static const struct tok gre_flag_values[] = {
65     { GRE_CP, "checksum present"},
66     { GRE_RP, "routing present"},
67     { GRE_KP, "key present"},
68     { GRE_SP, "sequence# present"},
69     { GRE_sP, "source routing present"},
70     { GRE_RECRS, "recursion count"},
71     { GRE_AP, "ack present"},
72     { 0, NULL }
73 };
74 
75 #define	GRE_VERS_MASK	0x0007		/* protocol version */
76 
77 /* source route entry types */
78 #define	GRESRE_IP	0x0800		/* IP */
79 #define	GRESRE_ASN	0xfffe		/* ASN */
80 
81 static void gre_print_0(netdissect_options *, const u_char *, u_int);
82 static void gre_print_1(netdissect_options *, const u_char *, u_int);
83 static int gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
84 static int gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
85 static int gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
86 
87 void
gre_print(netdissect_options * ndo,const u_char * bp,u_int length)88 gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
89 {
90 	u_int len = length, vers;
91 
92 	ND_TCHECK2(*bp, 2);
93 	if (len < 2)
94 		goto trunc;
95 	vers = EXTRACT_16BITS(bp) & GRE_VERS_MASK;
96         ND_PRINT((ndo, "GREv%u",vers));
97 
98         switch(vers) {
99         case 0:
100             gre_print_0(ndo, bp, len);
101             break;
102         case 1:
103             gre_print_1(ndo, bp, len);
104             break;
105 	default:
106             ND_PRINT((ndo, " ERROR: unknown-version"));
107             break;
108         }
109         return;
110 
111 trunc:
112 	ND_PRINT((ndo, "%s", tstr));
113 	return;
114 }
115 
116 static void
gre_print_0(netdissect_options * ndo,const u_char * bp,u_int length)117 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
118 {
119 	u_int len = length;
120 	uint16_t flags, prot;
121 
122 	flags = EXTRACT_16BITS(bp);
123         if (ndo->ndo_vflag)
124             ND_PRINT((ndo, ", Flags [%s]",
125                    bittok2str(gre_flag_values,"none",flags)));
126 
127 	len -= 2;
128 	bp += 2;
129 
130 	ND_TCHECK2(*bp, 2);
131 	if (len < 2)
132 		goto trunc;
133 	prot = EXTRACT_16BITS(bp);
134 	len -= 2;
135 	bp += 2;
136 
137 	if ((flags & GRE_CP) | (flags & GRE_RP)) {
138 		ND_TCHECK2(*bp, 2);
139 		if (len < 2)
140 			goto trunc;
141 		if (ndo->ndo_vflag)
142 			ND_PRINT((ndo, ", sum 0x%x", EXTRACT_16BITS(bp)));
143 		bp += 2;
144 		len -= 2;
145 
146 		ND_TCHECK2(*bp, 2);
147 		if (len < 2)
148 			goto trunc;
149 		ND_PRINT((ndo, ", off 0x%x", EXTRACT_16BITS(bp)));
150 		bp += 2;
151 		len -= 2;
152 	}
153 
154 	if (flags & GRE_KP) {
155 		ND_TCHECK2(*bp, 4);
156 		if (len < 4)
157 			goto trunc;
158 		ND_PRINT((ndo, ", key=0x%x", EXTRACT_32BITS(bp)));
159 		bp += 4;
160 		len -= 4;
161 	}
162 
163 	if (flags & GRE_SP) {
164 		ND_TCHECK2(*bp, 4);
165 		if (len < 4)
166 			goto trunc;
167 		ND_PRINT((ndo, ", seq %u", EXTRACT_32BITS(bp)));
168 		bp += 4;
169 		len -= 4;
170 	}
171 
172 	if (flags & GRE_RP) {
173 		for (;;) {
174 			uint16_t af;
175 			uint8_t sreoff;
176 			uint8_t srelen;
177 
178 			ND_TCHECK2(*bp, 4);
179 			if (len < 4)
180 				goto trunc;
181 			af = EXTRACT_16BITS(bp);
182 			sreoff = *(bp + 2);
183 			srelen = *(bp + 3);
184 			bp += 4;
185 			len -= 4;
186 
187 			if (af == 0 && srelen == 0)
188 				break;
189 
190 			if (!gre_sre_print(ndo, af, sreoff, srelen, bp, len))
191 				goto trunc;
192 
193 			if (len < srelen)
194 				goto trunc;
195 			bp += srelen;
196 			len -= srelen;
197 		}
198 	}
199 
200         if (ndo->ndo_eflag)
201             ND_PRINT((ndo, ", proto %s (0x%04x)",
202                    tok2str(ethertype_values,"unknown",prot),
203                    prot));
204 
205         ND_PRINT((ndo, ", length %u",length));
206 
207         if (ndo->ndo_vflag < 1)
208             ND_PRINT((ndo, ": ")); /* put in a colon as protocol demarc */
209         else
210             ND_PRINT((ndo, "\n\t")); /* if verbose go multiline */
211 
212 	switch (prot) {
213 	case ETHERTYPE_IP:
214 	        ip_print(ndo, bp, len);
215 		break;
216 	case ETHERTYPE_IPV6:
217 		ip6_print(ndo, bp, len);
218 		break;
219 	case ETHERTYPE_MPLS:
220 		mpls_print(ndo, bp, len);
221 		break;
222 	case ETHERTYPE_IPX:
223 		ipx_print(ndo, bp, len);
224 		break;
225 	case ETHERTYPE_ATALK:
226 		atalk_print(ndo, bp, len);
227 		break;
228 	case ETHERTYPE_GRE_ISO:
229 		isoclns_print(ndo, bp, len);
230 		break;
231 	case ETHERTYPE_TEB:
232 		ether_print(ndo, bp, len, ndo->ndo_snapend - bp, NULL, NULL);
233 		break;
234 	default:
235 		ND_PRINT((ndo, "gre-proto-0x%x", prot));
236 	}
237 	return;
238 
239 trunc:
240 	ND_PRINT((ndo, "%s", tstr));
241 }
242 
243 static void
gre_print_1(netdissect_options * ndo,const u_char * bp,u_int length)244 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
245 {
246 	u_int len = length;
247 	uint16_t flags, prot;
248 
249 	flags = EXTRACT_16BITS(bp);
250 	len -= 2;
251 	bp += 2;
252 
253 	if (ndo->ndo_vflag)
254             ND_PRINT((ndo, ", Flags [%s]",
255                    bittok2str(gre_flag_values,"none",flags)));
256 
257 	ND_TCHECK2(*bp, 2);
258 	if (len < 2)
259 		goto trunc;
260 	prot = EXTRACT_16BITS(bp);
261 	len -= 2;
262 	bp += 2;
263 
264 
265 	if (flags & GRE_KP) {
266 		uint32_t k;
267 
268 		ND_TCHECK2(*bp, 4);
269 		if (len < 4)
270 			goto trunc;
271 		k = EXTRACT_32BITS(bp);
272 		ND_PRINT((ndo, ", call %d", k & 0xffff));
273 		len -= 4;
274 		bp += 4;
275 	}
276 
277 	if (flags & GRE_SP) {
278 		ND_TCHECK2(*bp, 4);
279 		if (len < 4)
280 			goto trunc;
281 		ND_PRINT((ndo, ", seq %u", EXTRACT_32BITS(bp)));
282 		bp += 4;
283 		len -= 4;
284 	}
285 
286 	if (flags & GRE_AP) {
287 		ND_TCHECK2(*bp, 4);
288 		if (len < 4)
289 			goto trunc;
290 		ND_PRINT((ndo, ", ack %u", EXTRACT_32BITS(bp)));
291 		bp += 4;
292 		len -= 4;
293 	}
294 
295 	if ((flags & GRE_SP) == 0)
296 		ND_PRINT((ndo, ", no-payload"));
297 
298         if (ndo->ndo_eflag)
299             ND_PRINT((ndo, ", proto %s (0x%04x)",
300                    tok2str(ethertype_values,"unknown",prot),
301                    prot));
302 
303         ND_PRINT((ndo, ", length %u",length));
304 
305         if ((flags & GRE_SP) == 0)
306             return;
307 
308         if (ndo->ndo_vflag < 1)
309             ND_PRINT((ndo, ": ")); /* put in a colon as protocol demarc */
310         else
311             ND_PRINT((ndo, "\n\t")); /* if verbose go multiline */
312 
313 	switch (prot) {
314 	case ETHERTYPE_PPP:
315 		ppp_print(ndo, bp, len);
316 		break;
317 	default:
318 		ND_PRINT((ndo, "gre-proto-0x%x", prot));
319 		break;
320 	}
321 	return;
322 
323 trunc:
324 	ND_PRINT((ndo, "%s", tstr));
325 }
326 
327 static int
gre_sre_print(netdissect_options * ndo,uint16_t af,uint8_t sreoff,uint8_t srelen,const u_char * bp,u_int len)328 gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
329     uint8_t srelen, const u_char *bp, u_int len)
330 {
331 	int ret;
332 
333 	switch (af) {
334 	case GRESRE_IP:
335 		ND_PRINT((ndo, ", (rtaf=ip"));
336 		ret = gre_sre_ip_print(ndo, sreoff, srelen, bp, len);
337 		ND_PRINT((ndo, ")"));
338 		break;
339 	case GRESRE_ASN:
340 		ND_PRINT((ndo, ", (rtaf=asn"));
341 		ret = gre_sre_asn_print(ndo, sreoff, srelen, bp, len);
342 		ND_PRINT((ndo, ")"));
343 		break;
344 	default:
345 		ND_PRINT((ndo, ", (rtaf=0x%x)", af));
346 		ret = 1;
347 	}
348 	return (ret);
349 }
350 
351 static int
gre_sre_ip_print(netdissect_options * ndo,uint8_t sreoff,uint8_t srelen,const u_char * bp,u_int len)352 gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
353                  const u_char *bp, u_int len)
354 {
355 	const u_char *up = bp;
356 	char buf[INET_ADDRSTRLEN];
357 
358 	if (sreoff & 3) {
359 		ND_PRINT((ndo, ", badoffset=%u", sreoff));
360 		return (1);
361 	}
362 	if (srelen & 3) {
363 		ND_PRINT((ndo, ", badlength=%u", srelen));
364 		return (1);
365 	}
366 	if (sreoff >= srelen) {
367 		ND_PRINT((ndo, ", badoff/len=%u/%u", sreoff, srelen));
368 		return (1);
369 	}
370 
371 	while (srelen != 0) {
372 		if (!ND_TTEST2(*bp, 4))
373 			return (0);
374 		if (len < 4)
375 			return (0);
376 
377 		addrtostr(bp, buf, sizeof(buf));
378 		ND_PRINT((ndo, " %s%s",
379 		    ((bp - up) == sreoff) ? "*" : "", buf));
380 
381 		bp += 4;
382 		len -= 4;
383 		srelen -= 4;
384 	}
385 	return (1);
386 }
387 
388 static int
gre_sre_asn_print(netdissect_options * ndo,uint8_t sreoff,uint8_t srelen,const u_char * bp,u_int len)389 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
390                   const u_char *bp, u_int len)
391 {
392 	const u_char *up = bp;
393 
394 	if (sreoff & 1) {
395 		ND_PRINT((ndo, ", badoffset=%u", sreoff));
396 		return (1);
397 	}
398 	if (srelen & 1) {
399 		ND_PRINT((ndo, ", badlength=%u", srelen));
400 		return (1);
401 	}
402 	if (sreoff >= srelen) {
403 		ND_PRINT((ndo, ", badoff/len=%u/%u", sreoff, srelen));
404 		return (1);
405 	}
406 
407 	while (srelen != 0) {
408 		if (!ND_TTEST2(*bp, 2))
409 			return (0);
410 		if (len < 2)
411 			return (0);
412 
413 		ND_PRINT((ndo, " %s%x",
414 		    ((bp - up) == sreoff) ? "*" : "",
415 		    EXTRACT_16BITS(bp)));
416 
417 		bp += 2;
418 		len -= 2;
419 		srelen -= 2;
420 	}
421 	return (1);
422 }
423